For a considerable period of time, industry has relied upon a concept for preventative maintenance which is based upon the detection, analysis and the correction of vibration in monitored machinery. Initially, periodic vibration measurements were made at various locations upon industrial machinery to detect an increase in vibration which represented a signal that machine deterioration was at hand. An analysis of vibration was found to provide information which could indicate a malfunction so that proper corrective action would be taken. This general concept of preventative maintenance has grown considerably to the extent that, for many industrial facilities, vibration monitors are permanently installed and automatically monitored. In the course of such monitoring, somewhat complex systems are employed which isolate and collect a variety of vibrational parameter data such as displacement, velocity and acceleration. These data are stored, and the devices then carry out a trend analysis thereon. Such data and trend information then periodically may be displayed or printed out and/or plotted for the use of maintenance and operational personnel.
Size and cost factors associated with the above-noted more elaborate, multi-function equipment have resulted in a necessity or continuing need for less elaborate, function-limited and portable vibration analysis equipment. Generally, such portable equipment comprises a probe and pickup component or transducer which is coupled with an analog meter for providing a visual readout which may be observed by the operator. Such operators, particularly when acting as consultants or the like, investigate a multitude of machines at various probe locations thereon in the course of their endeavors, and each reading taken will be evaluated and the results hand recorded. In the latter regard, such readings also must be mentally interpreted with respect to scale factors and the parameters which have been measured prior to recordation. Thus, opportunities for human error readily arise.
The functional limitations of simple portable equipment also have been observed to limit the capability of the operator for achieving a high level of confidence in the analysis of machine vibrations. For instance, readings over a broad range or spectrum of vibrational frequencies are most desirable for analysis as are readouts taken over given intervals of time. In the latter regard, continuous monitoring during the start-up and/or coast-down intervals of machinery operation has been found to be quite useful.
To accommodate for certain of the above needs, portable, battery-powered, on-site vibrational analysis devices have been introduced. However, the flexibility of their use has been observed to be limited. For example, the devices operate in conjunction with slow, conventional ink-pin type x-y plotters and discrete readout cards containing universal graticules or graphics which, as before, must be interpreted mentally as to scaling factors, off-scale aberrations and the like. Further, their frequency spectral ranges are limited, and the number of vibrational parameters available with their use are quite restricted. Also unavailable to the operators of earlier devices has been a capability for generating a rapid printout curve of overall vibrational amplitude with respect to time during startup or coast down procedures. Such information can be quite valuable, certain machine defects being detectable only during these limited periods of operation.